As one whale swims past, another is revealed. Perhaps, it is rolling on its side to get a better view of the
photographer. Scientists onboard the Odyssey listen to 'clicks', the sounds that sperm whales make, to track sperm whales. These sounds give us
clues to social activities such as group aggregations.

This is Genevieve Johnson. The Odyssey crew is currently searching for sperm whales in the northern Bismarck Sea around Wewak. As usual, we are using our 300foot-hydrophone array, an underwater microphone to listen for the clicks of sperm whales. We can learn a lot about the lives of these whales by listening too and analyzing the sounds they emit. Visiting scientist Benjamin Kahn explains.

Benjamin Kahn:

So there is a wide array of uses that researchers have for these clicks. For instance we use clicks to track the whales, which is very basic in this voyage and in any sperm whale ecological research. We listen to the clicks passively and track them via a directional hydrophone. We can look for dive times and surface intervals, by looking at click patterns, by looking at when do the whales click and when do they stop clicking, which indicates that they are surfacing. We can look at abundance of sperm whales underwater, simply put, as one whale clicks at the rate of about two clicks per second, an underwater horse race of about twenty clicks per second, indicates ten echolocating, hunting whales. In addition, we can look at the presence or absence of mature males, because they too, have very distinctive and characteristic sounds. Finally, and perhaps the most tricky of all, we can estimate the body length of the clicking whale. A click characteristic called the 'inter-pulse' interval, is correlated to overall sperm whale length. This then relates to age, so we have overall demographics, very similar to how we would do this for a human population.

The codas too, have a lot of uses, the codas give us cues to likely social activities, such as group aggregations, when lots of different groups come together, sometimes forming major groups of fifty, or even one hundred or two hundred animals. Codas give cues to aerial behaviors, including lobtailing and breaches. Codas also give us a view of the change in dive routines of sperm whales and changes in foraging course for instance. So in a way, codas sometimes preclude a decision making process within the sperm whale community. The meeting and splitting up of groups, often have extensive and spectacular coda sessions associated with it.

Finally, we can measure regional connectivity by looking at coda dialects. So the monotonous sounding clicks coming through the hydrophone, is truly a window into sperm whale ecology. If you are only willing to listen, the sounds of the whales are research giveaways.

To learn more about the the sounds that sperm whales make, listen to the Odyssey Logs: